Choosing the Correct Marine Battery

With so many options in battery types and ratings it can be confusing trying to figure out what is the best battery for your boat. Choosing the correct product is dependent on the job the battery will have to perform.

If the batteries sole purpose is to start the engine, then you will want to choose a marine starting battery with the appropriate power for your engine.  The important rating for choosing an engine starting battery are Cranking Amps (CA) and Cold Cranking Amps (CCA), most marine batteries are rated in cranking amps as cold weather starting is rarely a requirement in marine applications and the higher the CA or CCA, the more available power the battery will have to start the engine.  Many of today’s new inboard engines and some larger outboards with fuel injection require batteries of 1000 CCA to perform properly while engines of smaller displacement do not require as much CCA or CA. 

Deep Cycle batteries should be used for operating house or auxiliary loads, the important rating on these types of batteries is Reserve Capacity (RC) or Amp Hour (Ah), the larger the RC or Ah the longer the battery will supply power to run auxiliary loads with the engine off.  Although deep cycle batteries may look similar to marine starting batteries, internally they have thicker plates that will handle more discharges and recharges that traditional starting batteries.  It should be noted that although deep cycle batteries are designed for deep discharges, these batteries should not be run below 80% of their rated capacity or overall life will be shortened.

The term Deep Cycle Marine Battery is often used to describe hybrid batteries or batteries that are designed to provide both starting and deep cycle functions.  These batteries do not usually provide the highest cranking amp or reserve capacity but work great for small vessels with 10-100 hp engines where the battery is also called upon to run auxiliary loads such as radios, lights, depth finders and live well pumps while the engine is off.

In all of these different marine starting, deep cycle and hybrid battery types there will often be the option of Absorbed Glass Mat (AGM) batteries, AGM batteries are a similar lead acid battery with the difference being the electrolyte inside the battery is absorbed in thick glass matt separators.  The advantage to AGM batteries over traditional flooded batteries is they require no maintenance and they do not off gas while charging or discharging which makes them much safer when operating them in confined areas with little or no ventilation.  AGM batteries are slightly more efficient and will recharge faster than flooded batteries, this is advantageous when recharging from the engine alternator to reduce engine run time and reduce fuel consumption.

Taking the time to choose the correct battery will help ensure that your boating experience is everything you expect from it.

Check out our video on the subject on our YouTube Channel!